In the hours and days after the Boston Marathon bombings, the Internet savvy snapped up domain names related to the tragedy, registering sites like BostonMarathonMassacre.com, whose profit-seeking owner posted “Buy This Site” over the widely published Associated Press photograph of Carlos Arredondo rushing alongside the wheelchair of Jeff Bauman Jr., who lost both of his legs.

That Monday alone, Go Daddy, the largest domain name registrar, experienced a 430 percent increase in registrations containing keywords such as Boston, marathon, or bomb, the company said. By Tuesday, registrations containing the same words had risen 555 percent.

Similar rushes happen around every major event — the naming of a new pope, Michael Jackson’s death, the Sandy Hook school shootings — for reasons both selfish and benevolent, according to analysts and others who work in the domain name industry. More often than not, registrants are hoping to land a domain that someone else will pay a lot to own.

But the odds of making a nice profit — especially with a name born out of a news event — are slim enough that the speculators who make their livings buying and selling domain names, wouldn’t bother at time like this, said Andrew ­Allemann, editor of DomainNameWire.com, an industry publication.

First, the relevance of domain names based on events tends to fade over time, and second, not many actually have a longstanding need for such sites, Allemann said. And then, many professional domain name dealers find the practice of trading on these types of events “tasteless.”

Some registrants, though, aren’t looking for money. Instead, they might just want control of a domain name that shows they were around ­during some big event, said Ari Goldberger, a ­domain name lawyer. And ­because domain names are a pretty cheap — about $10 a pop to hold a name for a year — it is affordable.

“It’s kind of like grabbing your piece of history, like grabbing an autograph from someone or getting a postcard or snapping a picture,” Goldberger said.

Others have good intentions, like Robert Cuda, the registrant of BostonMarathonBombers.com. Cuda, a computer programmer and stay-at-home dad in Texas, posted the FBI-released photos and videos of the bombing suspects in an effort to help authorities identify the men.

Cuda said he was prompted to act by a sense of loss and sympathy for those injured and killed in the blasts.

“These monsters want to ruin our joyous society by attacking innocents, usually in the course of the most wholesome activities,” Cuda said in an e-mail to the Globe. “These bombers knew what they were doing, and we can’t let people like that get the satisfaction of getting away with it.”

There’s also BostonMarathonConspiracy.com, which ­appeared just hours after the explosions tore through crowds near the Marathon finish line. The unknown registrant ­originally posted this message: “I bought this domain to keep some conspiracy theory kook from owning it.”

Now the message reads: “Please keep the victims of this event and their families in your thoughts. Thank you.”

Ed Rooney of Edgeworks Creative LLC, a Vermont print and Web design firm, registered BostonManhunt.com on something of a whim after mistyping “Boston bombs” as one word while searching for information last week, and being ­redirected to a news website.

“It was like, well, this is $10, may as well take it,” he said of the domain he eventually ­registered.

His initial thought: A media organization might want to buy the site. But Rooney said he’s now thinking of developing the site to create a timeline of last Friday’s events and collect people’s stories.

And then there are those who register domain names for fraudulent purposes, like setting up a fake charity — a big enough problem that specialists urge Internet users to be vigilant about which websites they frequent and to whom they give their credit card information.

Domain name registries are largely governed by policies ­developed and enforced by the industry. Those polices help ­resolve questions of ownership, defamation complaints, or ­infringing on a trademark or copyright, said Laurie Anderson, director of domain services at Go Daddy, which registers more than one domain name per second every day.

For instance, Anderson said, whoever registered BostonMarathonMassacre.com might have violated a copyright if they don’t have permission to use the AP photo posted on the site. Go Daddy, however, has not received such a complaint.

If Go Daddy were notified of a potential violation, Anderson added, “We would have the right to suspend that content of the website until such time as the content was taken down or the person filed a counterclaim stating they had the right to use that picture.”

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